This invention relates to a method and apparatus for comminuting and drying material utilizing a closed-loop cyclonic system including a cyclonic comminution chamber, and further incorporating heated or dried air for desiccation of the material, as well as reducing the air pressure of the system to provide enhanced drying of the material. The present invention further contemplates to a cyclonic mill system configured to fiberize and dewater cellulose and other materials in a highly efficient and cost effective manner.
The present system employs indirect heat drying and fiberizing for the continuous drying and processing of moist material including, for example, cellulose (i.e., paper, bagasse, etc) material by cyclonically agitating same in a hot air flow via a specially designed cyclonic mill, which is configured to effectively dewater and decimate wet cellulose and other materials from a variety of sources for form fiberized cellulose material suitable for thermal insulation. The present system contemplates a closed air cycle, recycling the heated air flow for energy conservation, while removing moisture and dust from same.
Although the cyclonic mill has been known and utilized in a variety of applications over the years, none of the prior art references found taught or suggested the system of the present invention. Further, prior art processes for the drying and fiberizing of cellulose or other materials for forming products such as, for example, insulation have proven to be highly energy intensive, dusty, and overall inefficient in practice.
Patents which may have some relevance to the general operative characteristics of cyclonic mills and the like may include:
The above patents can be categorized as 1) vacuum cominutors; 2) cyclonic dryers utilizing heated or dried air; 3) cyclonic material treatment processes; and 4) general interest patents on cyclone systems and related technologies.
U.S. Pat. Nos. 1,575,717, 4,892,261, 4,391,411, 3,255,793 and 5,421,524 contemplate the utilization of a possible vacuum in cyclonic systems for enhanced disintegration.
U.S. Pat. Nos. 4,236,321, 3,800,429, 1,830,174, 5,096,744, 4,756,093, 5,598,979 contemplate cyclonic dryers utilizing possibly heated or dried air. Note that ""979 further discusses the implementation of an xe2x80x9cairlockxe2x80x9d to further processing of the material.
U.S. Pat. No. 5,074,476, entitled xe2x80x9cMethod of manufacturing Fiber Material Containing Lignocellulose for the Production of Fiber boardsxe2x80x9d, contemplates a cyclonic material treatment process which may have some pertinence to the present cellulose treatment. U.S. Pat. No. 4,187,615 is cited as of interest in that it incorporates a corona field in the treatment stream, which may be of use in the future for your system in some applications. U.S. Pat. No. 3,937,405 is of general pertinence teaching a cyclonic system for finely grinding powder.
The remaining patents above are cited for general information purposes, teaching cyclonic systems and related technologies.
Production of cellulose insulation products is not new, and is discussed in U.S. Pat. Nos. 4,168,175 to Shutt and 4,595,414 to Shutt and 5,534,301 to Shutt, which are further mentioned herein for reference.
In the prior art processes involving all-liquid fire retardant and drying chamber systems, which are entirely free of any fire retardants in a powder (dry) form, see U.S. Pat. No. 5,534,301 to Shutt. A supply of cellulose xe2x80x9cpaperxe2x80x9d (preferably xe2x80x9cgrade 8xe2x80x9d newspaper) is selected. The paper materials (i.e., recycled newspaper) are loaded into one or more conventional shredding and/or grinding systems to produce pieces of paper having a average width of about 2-6 in. and an average length of about 2-6 in. These numerical values are preferred for use in the claimed process.
The pieces of paper are transferred into a conventional spraying apparatus in which a liquid fire retardant is applied to the paper. As a result, fire retardant soaked paper product is generated. The product is then transferred into air that is heated to a temperature of about 300-350 deg. F. at a flow rate of 2500-3500 feet/minute designed to simultaneously move paper product within chambers controlled with baffles to delay the paper product in the chambers to sustain a level of air flow or contact time with the paper product. The dried paper material is further processed to achieve additional size reduction. Size reduction is accomplished using one or more hammer mills or fiberizer systems known in the art for this product. The completed insulation product is then packaged and sold.
Another concept in drying of moist product is represented in U.S. Pat. No. 3,592,395 to R. M. Lockwood wherein a fluidized bed dryer is provided to stir and dehydrate the product by motion of air through the product and in conjunction with a rotary agitator to stir the product.
Another drying apparatus for this type of material is shown in U.S. Pat. No. 4,070,765 to S. Hovmand et al wherein a pneumatic conveyor dryer is used in the drying. This apparatus also includes recycling a portion of the dried material.
The deficiencies in the prior art equipment and processes involving drying cellulose insulation product lie in the need for continuous drying and the dust removal aspect xe2x80x9cnot making more dustxe2x80x9d. While the above noted processes could possibly be used to dry cellulose insulation product, they would be inefficient in that, after drying the fire retardant soaked paper product, the dry paper material would have to be further processed to achieve an approved level of smolder resistance, radiant panel, settle density, blown density, dust level and R-value.
In the prior art processes involving dry powder fire retardant system, a supply of cellulose xe2x80x9cpaperxe2x80x9d (preferably xe2x80x9cgrade 8xe2x80x9d newspaper) is selected. The paper materials (i.e. recycled newspaper) are then loaded into one or more conventional mechanical devices such as hammer mill systems known in the art to produce a pulverized product that is then sent to a fiberizer to produce a finely divided cellulose insulation product which maybe blended with a dry powder fire retardant to produce the completed product. The completed insulation product is then packaged and sold.
The deficiencies in the prior art equipment and processes using a dry powder fire retardant system are (a) the paper materials selected have to be dry and of a good quality and thereby expensive and selective (i.e., recycled newspaper preferably xe2x80x9cgrade 8xe2x80x9d newspaper); these types of processes are sensitive to moisture; (b) they require the use of expensive, energy intensive additional devices such as hammer mill systems; (copyright) they further require the use of a fiberizer to produce a finely divided cellulose insulation product to add the selected dry powder fire retardant; (d) the need to use large amounts of dry fire retardants due to production with powder-type systems; e) Increase cost associated with the need to use large amounts of powder chemicals; (f) high amount of dust associated with dry powder systems.
This type of multi-stage size reduction by grinding or other conventional means requires high energy consumption and equipment which requires high maintenance and excessive down time.
Unlike the prior art, the present invention contemplates a relatively easily implemented, energy efficient and cost effective indirect heat drying and fiberizing system for the continuous drying of material by cyclonic agitation in a hot air flow, utilizing hot air being recycled with moisture and dust removed from the recycled air, providing substantially dry, fiberized or pulverized material without further processing.
The present invention can be used to produce cellulose products including as well as other diverse products utilizing cellulose, which can come from various organic sources as well as recycled materials such as waste paper, bagasse, as well as other materials, which can be fiberized, pulverized, and dewatered.
In the preferred embodiment of the present invention, indirect hot air is provided and a blower is connected tangentially to a double conical chamber through a nozzle, producing a cyclonic flow of high velocity air, such that the high velocity of the material entering the conical chambers is placed under tension and tends to fracture along areas of weakness such as boundary layers (fiberization) and the larger heavier particles are forced to the outer layers and the lighter or dryer particles are forced to the middle and down the wall of the conical chambers into a lower pressure area (vacuum) at the appropriate speed so that, with the abrupt change in pressure, the material is suddenly reversed upwards.
The average velocity determines the rate of evaporation since the transfer of heat to the surface depends on velocity. The heat transfer coefficient varies with velocity, and is a measure of resistance per unit area, as in the resistance to the flow of heat through a thin layer of the surface.
The present invention involves the mixing, agitating and separating of the material in thin layers (fiberizing), in a cyclonic hot air flow that is below atmospheric pressure while regulating the flow of moist material and the moisture removal from the air in order to dehydrate the moist material to a dry and fiberized cellulose insulation product having less than about 10% percent moisture content by weight, and separating dried material from the air flow in a product separator and separating moisture and dust from a portion of the air stream in a waste product separator and recycling the remainder of the hot air into the conical chamber. The present system can be used to dry and fiberize cellulose to provide, for example, insulation that will meet the approved level of smolder resistance, radiant panel, settle density, blown density and R-value.
The materials are carried from the conical chambers in the hot air flow and separated from the hot air flow in a cyclone separator The cyclone separator discharges dried material into a storage container for bagging. Hot air from the cyclone separator has a portion extracted for dust and moisture removal prior to being recycled into the conical chambers.
One object of this invention is to overcome the disadvantages of the prior art devices in drying moist particulate and in the product on of cellulose insulation.
Still another object of this invention is to provide a processing apparatus that will operate continuously to dry moist particulate that has a liquid fire retardant composition soaked, sprayed, or washed into the fiber in the process of making cellulose insulation.
Still another object of this invention is to provide a process apparatus which is capable of handling this moist fiber and pulverizing it into a finely divided insulation.
Still another object of this invention is to provide an apparatus which is capable of producing a less dusty cellulose insulation.
Still another object of this invention is to provide an apparatus which is more versatile than prior art in selecting and mixing of raw materials. Example: you would have to buy #8 newspaper and in some cases you are paid to take the lower grades.
Still another object of the present invention is to provide a system for treating diverse materials including various cellulose products including paper, bagasse, straw, flax, and other cellulose and other organic or inorganic materials, to pulverize, dewater, and/or fiberize same using a more efficient and effective system than the prior art.